rc/sh/maybesudo

#!/usr/bin/env sh
# compat: +ash +bash +dash -hush -ksh +mksh +oksh +osh +posh +yash +zsh

__maybesudo() { ### @maybesudo
    ### mimic certain features of `sudo` for systems without it installed.
    ### as it stands, this mostly just handles some environment variables.
    ###
    ### try this: `maybesudo -u "$USER" printenv`

    complain() {
        printf >&2 'maybesudo: %s\n' "$*"
    }

    usage() {
        printf %s\\n \
        'maybesudo - a dumb utility for systems without sudo' \
        '' \
        'usage: maybesudo -h | -V' \
        'usage: maybesudo [-u user] command [arg ...]' \
        'usage: maybesudo [-u user] file ...' \
        ;
    }

    name=
    env_cleanup=0

    while getopts :AEHKPSVbhiklnsvC:U:g:p:r:t:u: name; do
        case "$name" in
        ([KVk])
        # K: sure kill
        # V: version
        # k: kill
            complain 'your system does not have sudo installed!'
            return 0
            ;;

        (h)
            usage
            return 0
            ;;

        ([AEHPSnp])
        # A: askpass
        # E: preserve environment
        # H: HOME
        # P: preserve group vector
        # S: stdin (password)
        # n: non-interactive
        # p: prompt
            complain 'option has no effect --' "'$name'"
            ;;

        ([CUbgilrstv])
        # C: close from (fd)
        # U: other user (in conjunction with -l)
        # b: background
        # g: group
        # i: simulate initial login (TODO)
        # l: list
        # r: role (SELinux)
        # s: shell (TODO)
        # t: type (SELinux)
        # v: validate
            complain 'unsupported option --' "'$name'"
            return 1
            ;;

        (u) # user
            if [ -z "$USER" ] || [ "$OPTARG" != "$USER" ]; then
                complain 'users other than yourself are unsupported!'
                return 1
            fi
            env_cleanup=1
            ;;

        (:)
            complain 'option requires an argument --' "'$OPTARG'"
            return 1
            ;;
        (*)
            complain 'invalid option --' "'$OPTARG'"
            return 1
            ;;
        esac
    done

    shift "$((OPTIND-1))"

    if [ $# = 0 ]; then
        usage >&2
        exit 64 # EX_USAGE
    fi

    if [ "$env_cleanup" = 1 ]; then
        # portably listing exported variable names is virtually impossible
        # without the blessing of null-terminated strings, so don't even try.
        # just export the bare minimum that a fairly stock sudo would.
        # TODO: you know, awk has an ENVIRON array that might be easier to work with.

        # don't eat up precious command space with dumb colors.
        # xargs --show-limits says:
        # Maximum length of command we could actually use: 5080
        [ "${#LS_COLORS}" -le 1024 ] || LS_COLORS=

        # doas seems to override PATH with /bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
        # sudo also sets SUDO_COMMAND, SUDO_GID, SUDO_UID, SUDO_USER, and MAIL,
        # but who needs those?
        #   "${USER:+DOAS_USER=}${USER}"
        #   "${USER:+SUDO_USER=}${USER}"
        #   "${LOGNAME:+LOGNAME=}${USER:--i}"

        [ -z "$XAUTHORIZATION" ] || set -- XAUTHORIZATION="$XAUTHORIZATION" "$@"
        [ -z "$XAUTHORITY" ]     || set -- XAUTHORITY="$XAUTHORITY" "$@"
        [ -z "$USERNAME" ]       || set -- USERNAME="$USERNAME" "$@"
        [ -z "$USER" ]           || set -- USER="$USER" "$@"
        [ -z "$TERM" ]           || set -- TERM="$TERM" "$@"
        [ -z "$SHELL" ]          || set -- SHELL="$SHELL" "$@"
        [ -z "$PATH" ]           || set -- PATH="$PATH" "$@"
        [ -z "$LS_COLORS" ]      || set -- LS_COLORS="$LS_COLORS" "$@"
        [ -z "$KRB5CCNAME" ]     || set -- KRB5CCNAME="$KRB5CCNAME" "$@"
        [ -z "$HOSTNAME" ]       || set -- HOSTNAME="$HOSTNAME" "$@"
        [ -z "$HOME" ]           || set -- HOME="$HOME" "$@"
        [ -z "$DPKG_COLORS" ]    || set -- DPKG_COLORS="$DPKG_COLORS" "$@"
        [ -z "$DISPLAY" ]        || set -- DISPLAY="$DISPLAY" "$@"
        [ -z "$COLORS" ]         || set -- COLORS="$COLORS" "$@"
        set -- -i "$@"

    elif ! [ -d /C ]; then # no such thing as sudo on Windows (kinda)
        complain 'you requested root permissions, but you do not have sudo installed.'
        return 69 # EX_UNAVAILABLE
    fi

    exec env "$@"
}

maybesudo_()(__maybesudo "$@") # deprecated

[ -n "${preload+-}" ] || . ~/sh/preload || exit 2
eval ${preload:-preload} has

if has sudo; then
    maybesudo() { sudo "$@"; }
elif has doas; then
    maybesudo() { doas "$@"; }
else
    maybesudo() (__maybesudo "$@")
fi

[ -n "${preload+-}" ] || __maybesudo "$@"